WHO Says Ebola Virus May Be More Widespread Than Thought

The World Health Organization is expressing concern that ``an invisible caseload'' of Ebola patients is going undetected by government surveillance measures in West Africa.

In a situation assessment issued today, the WHO notes that treatment centers opened over the past two weeks in Liberia were immediately overwhelmed by patients that had not been identified previously. That situation, it says, has ``never before been seen in an Ebola outbreak'' and suggests the scale of the outbreak is being underestimated, especially in Liberia and Sierra Leone.

Earlier this week, the WHO put the death toll at more than 1,300. Hundreds of cases have been reported in Guinea and Sierra Leone, while Liberia has seen the most deaths with 576.

A total of 213 people are under surveillance in Nigeria, where officials reported two new cases today. The country's health minister says the patients are the spouses of a man and woman who had cared for Patrick Sawyer. The Liberian-American was already infected with Ebola when he flew into Nigeria last month. He infected 11 others before he died.